This invention relates to a furl supplying apparatus mounted within a fuel tank of an automobile or the like for supplying fuel under pressure to an injector which injects fuel to an engine.
FIG. 5 is a sectional side view of the conventional fuel supplying apparatus disclosed in International Publication No. WO96/23967.
In the figure, a fuel supplying apparatus 1 which comprises as an assembly a cover 3, a fuel pump 4, a fuel filter 5, a pressure regulator 6, a discharge pipe 7, an unillustrated fuel level indicator and an unillustrated electrical connector is suspended from an opening 2a of a fuel tank 2 made of a metal or a resin.
The fuel filter 5 comprises a holder member 5a made of an electrically conductive resin and a filter element contained therein and is welded to a boundary 8 between the cover 3 in a liquid-tight manner. The holder member 5a holds the fuel pump 4 at its central portion and the pressure regulator 6 at the lower end portion. A gasket 9 for the gas-tight seal is interposed between the cover 3 and the fuel tank 2.
In the holder member 5a of the fuel filter 5, an inlet portion 10 as a fuel inlet for the fuel filter 5 is disposed at the upper portion of the inner circumference of the holder member 5a and is connected to the discharge pipe 11 of the fuel pump 4 through a seal 10a. Also, the holder member 5a of the fuel filter 5 has two fuel outlets, a pipe 12 (shown by a dot-and-dash line) constituting the first fuel outlet extending axially upwardly from the bottom end of the holder member 5a. The pipe 12 is connected to the discharge pipe 7 to supply the filtered fuel to the injector. A return path 13 constituting the second fuel outlet is disposed at the lower portion of the holder member 5a and is connected to the pressure regulator 6.
14 is a strainer for filtering fuel before it is suctioned into the fuel pump 4 against any foreign matters such as iron powders within the fuel tank 2.
The pressure regulator 6 is inserted at its base 6a into insertion portion 5c extending downwardly from the bottom of the holder member 5a and is fixed thereto. A diaphragm 6c is held between the open end of the housing 6a and the housing 6b, and the diaphragm 6c supports a movable valve seat 6e having an discharge hole 6d. 
Within the base 6a, a stationary valve seat 6f that co-operates with the movable valve seat 6e is fixed. Between the housing 6b and the diaphragm 6c, a spring 6g is received and a exhaust port 6h for discharging the fuel from the discharge hole 6d into the fuel tank 2 is disposed at the lower portion of the hosing 6b. 
4a a current supply unit for supplying an electric current to an unillustrated motor of the fuel pump 4 and electrically connected to an unillustrated electrical connector integrally formed with the cover 3.
In the fuel supply apparatus thus constructed 1, when an electric current is supplied to the unillustrated motor of the fuel pump 4 from the unillustrated electrical connector through the current supply portion 4a, the motor rotates, and the fuel within the fuel tank 2 is suctioned through the strainer 14 and after discharged from the discharge pipe 11 flows through a passage 15 in the direction of an arrow A to pass through the filter element 5b to reach to a lower space 16 defined under the filter element 5b. 
One part of the fuel is flowed into the pressure regulator 6 and, when the fuel pressure becomes higher than the set pressure of the spring 6g, the diaphragm 6c is moved toward the housing 6b to open the discharge hole 6f of the movable valve seat 6e so that the fuel within the base 6a is returned through the discharge port 6h to the fuel tank 2 again. The other part of the fuel flows through the pipe 12 in the direction of an arrow B to be supplied to the injector of a fuel injection apparatus mounted to an unillustrated engine through the discharge pipe 7.
In the conventional fuel supplying apparatus, the motor of the fuel pump 4 is supplied with a constant continuous electric power so that a constant amount of fuel is pumped from the fuel tank 2, and the fuel demanded by the injector associated with the engine is supplied through the discharge pipe 7 and the excessive amount of fuel is all returned to the fuel tank 2 from the discharge hole 6d of the pressure regulator 6 through the discharge port 6h. 
The fuel pump 4 is set to pump an amount of the fuel equal to or more than that required by the engine at the time of the maximum load. However, the fuel amount required by the engine injector during idling is small, so that most of the pumped fuel is returned to the fuel tank 2 through the discharge port 6h of the pressure regulator 6.
As discussed above, the fuel pump motor is always driven at the full power irrespective of the fuel amount required by the injector, so that the electric current consumption of the fuel pump 4 is high and the load to the battery mounted on the vehicle is high. Also, since the motor of the fuel pump 4 is operated at a high speed even when the engine noise is low such as during the idling, the operating noise of the fuel pump 4 is high.
This invention has been made to solve the above-discussed problems and has as its object the provision of a fuel supplying apparatus in which the fuel pump is operated to discharge an amount of the fuel corresponding to the fuel amount required by the injector, whereby the current consumption of the fuel pump is reduced and the operating noise is lowered.
The fuel supplying apparatus of the present invention comprises a cover portion installed to an opening portion of a fuel tank and having an outlet pipe disposed thereon, a fuel pump for pumping fuel within the fuel tank to an injector of an engine through the outlet pipe, a fuel filter for filtering the fuel discharged from the fuel pump, and a fuel pressure regulator for detecting the pressure of the fuel discharged from the fuel pump and regulating the discharge pressure of the fuel discharged from the pump according to the detected fuel pressure.
The fuel pressure regulator may comprise a fuel pressure detection portion and a current control portion for controlling the current flowing through the fuel pump according to a signal from the fuel pressure detection portion.
The fuel pressure regulator may comprise a diaphragm portion displaceable in response to the fuel pressure, a compression spring for adjusting the displacement amount of the diaphragm portion and a shaft for guiding the movement of the diaphragm in a predetermined direction.
The current control portion may be composed of an analogue circuit comprising a variable resistor of which resistance varies according to the amount of displacement of the shaft, and a transistor of which base current is controlled according to the variable resistor.
Further, the present invention resides in a fuel pressure regulating apparatus comprising a suction portion for suctioning fuel, a fuel pressure detection portion for detecting fuel pressure, and a current control portion for controlling a current flowing through a fuel pump according to a signal from the fuel pressure detection portion.